This project will investigate the immunologically nonspecific processes by which accessory cells regulate the functions of immunocompetent lymphocytes. Particular attention will be given to developing improved methods for obtaining purified populations of accessory cells and for measuring their immunopotentiating activities. Several adjuvants will be used to stimulate the production of biologically active factors by accessory cells. The resulting factors will be examined by several different bioassays to help identify possible heterogeneity of accessory cell types and functions. The effects of accessory cell factors in causing T lymphocytes to modulate their responses to glucocorticosteroids will be investigated intensively to develop better assays and to develop insights about the mechanisms of this intriguing example of cell-cell interaction.